The preceding example shows that accurate representation of fuel-cycle performance requires such detailed examination of the time-varying changes in power distribution and fuel composi­tion at many points in a nuclear reactor as to necessitate use of a digital computer. The purpose of this section is to develop an approximate procedure for calculating fuel-cycle performance that, although complicated, can be carried out by hand calculation. The PWR described in Sec. 4.1 will be used as example, except that its rated electric output is taken as 1054 MWe instead of 1060 MWe.